Also you can do this via Child Theme.
Please copy file into it saving folder structure like:
wp-content/themes/Legenda_child/woocommerce/includes/abstracts/abstract-wc-order.php and there make changes.
I’m using the Woocommerce translation package for German language at this site. It seems to be a mainstream component / up-to-date so it would be weird if they skipped the string “Subtotal” which is included in the Woocommerce checkout process per default. However, I just added another – less mainstream – package for German language to test things.
I’ll look into this and report back.
Sure. But the upgrade path would still be compromised that way.